This invention relates to a fuel supply system for direct injection engines and more particularly to an improved high pressure fuel pump for an outboard motor incorporating a direct injection system.
As is well known, in all fields of engine design there is an increasing emphasis on obtaining more effective emission control, better fuel economy and, at the same time, continued high or higher power output. This trend has resulted in the substitution of fuel injection systems for carburetors as the engine charge former. In order to obtain still further improvements, direct fuel injection systems are being considered. These systems inject fuel directly into the combustion chamber and thus have significant potential advantages.
In many applications, the incorporation of direct injection is relatively straightforward. However, in connection with outboard motors, the very compact nature of the outboard motor renders this further sophistication in engine design difficult to obtain. The problems in connection with direct fuel injection systems for outboard motors is related primarily to the space that is.
These problems arise, in part, because of the number of components required for fuel injection and the very nature of some of these components. For example, with manifold injection systems for outboard motors, it has been the practice to provide a fuel injection system that includes at last the following components:
a low pressure fuel pump,
a high pressure fuel pump,
a pressure regulator,
a vapor separator; and
a fuel rail for delivering the fuel to the injectors.
The use of a vapor separator is required primarily because of the confined space and the fact that fuel vapors or air in the fuel, conditions primarily resulting from heat, can cause erratic injection and poor performance.
For the same reasons, it has also been the practice to position the high pressure fuel pump in the vapor separator so as to permit it being cooled and to minimize the amount of heat that is generated in the system and to remove the heat from the fuel that is delivered to the injectors. This also saves space. However, this necessitates the use of an electrically operated fuel pump. Such pumps have limited capacity in the pressure which they can generate.
With direct injection systems, however, the fuel must be injected directly into the combustion chamber. This means that the pressure into which the fuel is injected is higher than with manifold injection systems wherein the pressure is at substantially atmospheric or even below. Electric pumps are not totally capable of supplying such high pressures. Thus engine driven, mechanical pumps are required.
In conjunction with the use of these mechanical pumps, the pump configuration may at times require the use of a transmission to drive the pump. That is, the type of pump employed may have its axis positioned in a position that is not parallel to the axis of rotation of the engine output shaft. Thus, bevel gear transmission or other mechanical transmissions may be required in order to transmit the drive from the engine output shaft or another shaft driven by it and the pump input shaft.
Both the mechanical pump itself and the driving transmission can generate heat. Unless this heat is dissipated externally in another fashion, the heat may actually be transmitted to the fuel and cause vapor problems.
It is, therefore, a principal object of this invention to provide an improved high-pressure fuel pump for an internal combustion engine and particularly one that is utilized in conjunction with an outboard motor.
It is a still further object of this invention to provide an improved high-pressure fuel pump and drive therefor for a fuel injection system wherein the fuel pump is cooled externally.
It is a still further object of this invention to provide an improved high-pressure fuel pump for a fuel injection system for an internal combustion engine that shares a cooling system with the engine cooling system.
This invention is adapted to be embodied in a fuel injection system for an internal combustion engine. The engine is provided with a cooling jacket that is supplied with cooling water. A fuel injection system is provided for the engine and this includes fuel injectors for injecting fuel directly into the cylinders of the engine. A fuel supply system supplies high-pressure fuel to the fuel injection system. This includes a high-pressure pump and a transmission for driving the high-pressure pump from an engine output shaft. A cooling jacket is provided for at least one of the high-pressure pump and its transmission and coolant delivered to the engine cooling jacket is also supplied to this fuel pump cooling jacket.